1. Field of the invention
The present invention relates in general to a system and method for automatically distinguishing between graphic information and text information of image data, and more particularly to a system for automatically distinguishing between graphic information and text information of image data, by use of grayscale levels and in a simple manner which binarizes the image data, so that the graphic and text of the image are clearly represented.
2. Description of the Prior Art
Known prior art techniques for distinguishing between graphic information and text information of image data are disclosed in U.S. Pat. Nos. 4,577,235 and 4,554,593.
First, grayscale image data obtained by scanning a document to be duplicated is partitioned into contiguous image data blocks (for example, four pixels by four pixels) which are processed to determine whether the portions of the image represented by the data blocks corresponds to text or graphic portions of the document. An average grayscale value is determined for each data block and used as an indexing variable for at least one additional characteristic determined for the block. Additional characteristics include a block variance, a block edge count, a block agreement count and a block text average. A one dimensional Gaussian Distribution is generated to distribute the data values of any additional characteristics for each possible grayscale value of a block. The mean and standard deviation are determined for each data distribution and Mahalanobis distance for each characteristic data value is determined. The Mahalanobis distance is a representative probability for whether the image data block corresponds to a text portion of the image or a graphic portion of the image.
Gaussian distributions are generated for both text data and graphic data such that probabilities for both text and graphic can be estimated independently for each image data block. The text probability is then normalized by dividing it by the sum of the two probabilities. The normalized text probability is then utilized to determine whether the data blocks correspond to text or graphic portions of the image.
However, the above-mentioned conventional technique for distinguishing graphic/text portions from each other has a disadvantage of the overloaded software and thus the delayed data determination speed, since the characteristic of block classified into four types is adopted to the distinction of graphic/text portions. In constituting a system which processes input signal within the real time to achieve the distinction of graphic/text portions, there is a problem of the delay of real time corresponding to 9 blocks (36 lines), in that the environment is subjected to a cross type scanning which involves a vertical scanning to a maximum of nine blocks and a lateral scanning to a maximum of nine blocks.